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Mercedes VGS3-FDCT (TCM9 FDCT): TCU personalisation and dedicated DB25 cable

Mercedes Interface New Keys / Immo Advanced ⏱ 1-2 hours 14 steps

Replacing a VGS3-FDCT (TCM9 FDCT) transmission control unit: reading and saving the FBS4 data from the original, virginising the donor and personalising it, plus the wiring diagram for the custom DB25 cable used for the direct connection.

Required licences

  • —

Hardware / cables

  • AVDI
  • DB25 maschio
  • alimentatore esterno 12V
⚠ WarningSize the power supply according to what you have in front of you: working on the TCU conductor plate alone you need an external 12 V supply rated at least 1 A; if the plate is still in the gearbox and connected through the socket, you need a 12 V supply rated at least 4 A. On this TCU the VIN must be set BEFORE "Personalize". Activation happens automatically after 100 ignition cycles.

Procedure

  1. Make up the custom cable with a male DB25 connector: CAN L of the TCU connector to PIN 15 of the DB25 going to the AVDI; CAN H to PIN 7; B+ 12 V to PIN 17; GND- to PIN 5 and 6.
  2. Solder the external supply wires onto the male DB25: +12 V to Pin 17, ground (GND) to Pin 4 and 5.
  3. Choose the power supply: 12 V rated at least 1 A if you are working on the conductor plate alone, 12 V rated at least 4 A if the plate is still in the gearbox and connected through the socket.
  4. READING - Connect the original TCU over OBDII on the car or on the bench, open the Mercedes FBS4 Manager software and select "TCU".
  5. Press "Info" to establish the connection, then "Save" to read and save the FBS4 data to file.
  6. Back up the configuration: TCU > "Utilities" > "Save All Config Data". This data, along with the FBS4 data, is what you need to personalise the replacement unit properly.
  7. PERSONALISATION - Set the donor up on the bench with the custom cable described above.
  8. Open the Mercedes FBS4 Manager software, select the "TCU" option and press "Info" to establish the connection.
  9. Take the unit to "Virgin" state with the dedicated button. If the TCU is already virgin or brand new, skip straight to the next step. From here you can either carry on in the car over OBDII and internal CAN, or stay on the bench.
  10. Set the VIN of the car.
  11. Press "Personalize" and select the file with the FBS4 data saved from the original TCU.
  12. When prompted, cycle the key IGN OFF and then ON to finalise the procedure.
  13. Program the configuration data with "Utilities" > "Program All Config Data" using the files saved from the original.
  14. Bear in mind that the unit activates automatically after 100 ignition cycles.

Reference screenshots

Mercedes VGS3-FDCT (TCM9 FDCT): TCU personalisation and dedicated DB25 cable — 1Mercedes VGS3-FDCT (TCM9 FDCT): TCU personalisation and dedicated DB25 cable — 2
Source: Manuale Mercedes FBS4 Manager, parte 2 di 2, cap. 5.4.1 e 5.4.2 (p.57-58) · ⏱ estimated time 1-2 hours
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